The present invention relates to a motor-vehicle door latch. More particularly this invention concerns a power-actuated motor-vehicle door latch.
A power-actuated door latch, for instance used on a motor-vehicle trunk and as described in German patent document 196 50 826 of Bartel and Kleefeldt, has a housing, a lock fork pivotal on the housing between open and closed positions, a latch pawl pivotal on the housing and engageable with the fork in the closed position to retain it therein and disengageable from the fork to allow to move from the closed to the open position, and an opening lever coupled to the latch pawl and displaceable between an actuated position displacing the latch pawl out of engagement with the fork and an unactuated position with the latch pawl engageable with the fork. A rotary drive is coupled to the opening lever for displacing it between its actuated and unactuated positions. German utility model 86 21 592 describes a linear actuator used in such a system. With such a structure a switch is actuated by the vehicle operator to energize the drive and open the latch, normally without requiring any further action to be taken before the door can be pulled fully open or the trunk lid fully raised.
An annoying feature of these systems is that, once the door is released so it can be opened, the drive for the latch continues to rotate so that it can move back into its starting position. Thus after the click produced by the release of the door, there is the grinding sound of the motor and gear train as the drive is returned to its starting position. This starting position must be reassumed so that the latch can be closed again, as if the drive stopped just when it had released the fork, the pawl would be retained in a position spaced from the fork and would not arrest the fork when the door were closed again. Furthermore such latches are often unnecessarily complex.
It is therefore an object of the present invention to provide an improved power-actuated motor-vehicle door latch.
Another object is the provision of such an improved power-actuated motor-vehicle door latch which overcomes the above-given disadvantages, that is which operates quietly and that is of simple construction.
A motor-vehicle door latch has according to the invention a housing, a lock fork pivotal on the housing between open and closed positions, a latch pawl pivotal on the housing and engageable with the fork in the closed position to retain it therein and disengageable from the fork to allow to move from the closed to the open position, and an opening lever coupled to the latch pawl and displaceable between an actuated position displacing the latch pawl out of engagement with the fork and an unactuated position with the latch pawl engageable with the fork. A rotary drive couplable to the opening lever can displace it between its actuated and unactuated positions. In accordance with the invention structure engageable between the fork and the opening lever decouples the opening lever from the drive on displacement of the fork from the open to the closed position.
Thus with this system as the latch is closed, the fork itself mechanically decouples the opening lever from the drive, thereby allowing to move, normally by spring force, back into the unactuated position in which the pawl is again engageable with the fork. As a result the drive can stop when the opening lever is moved into the actuated position, since when the latch is closed the opening lever is decoupled from the drive and moved by its spring back into the unactuated position by the fork. Whatever the drive is doing or whatever position it is in, is irrelevant during the closing operation when the drive is disconnected from the opening lever and locking pawl. Once opened, the door can always be closed and latched, regardless of what the drive is doing. This is in contrast to the prior-art systems where the drive had to cycle somewhat after opening so that if a user immediately closed the door after it opened, the latching would be incomplete or not take place.
According to the invention the drive includes a formation orbital about an axis and the opening lever has a seat open tangentially of the axis and in which the formation is seatable to displace the opening lever from the unactuated position to the actuated position. In addition the drive includes a wheel rotatable about the axis and carrying the formation and an electric motor and gearing connecting the motor to the wheel. With worm gearing a small and very quiet rotary motor can be used to power the latch.
The decoupling structure includes a pin projecting from the opening lever and a cam on the fork. It also includes a cutout lever pivoted on the housing and having formations engageable with the cam of the fork and the pin of the opening lever. These formations include a pin engageable with the cam and a cam edge engageable with the opening-lever pin. Thus the addition of a single one-arm lever to the structure allows the fork to decouple the opening lever from its drive and greatly simplifies and rationalizes operation of the latch.
The spring urging the opening lever into the unactuated position and urging the pawl into engagement with the fork also serves to decouple the seat from the orbital drive formation so that when the decoupling mechanism releases the opening lever, once the latch is closed, the seat is behind the orbital formation and the drive is again clear for movement. Thus a cheap unidirectional motor can be used in the drive.
In accordance with the invention a lost-motion coupling supports the opening lever on the pawl and permits the opening lever to move limitedly relative to the pawl. It includes a slot extending tangentially of the axis and a pin fitting in the slot. The slot is formed according to the invention on the opening lever and the pin is fixed on the pawl.
The housing is provided with a pair of fixed abutments and the opening lever is engaged with one or the other of them in its actuated and unactuated positions. One of these abutment can be a simple stop fixed on the housing and engageable with an end of the opening lever. The other can be the shaft on which the wheel carrying the orbital formation is mounted, since the surface of this shaft, even if it rotates, does not move in the tangential direction the opening lever moves in between its actuated and unactuated positions.